Not applicable.
1. Technical Field
This invention relates to the field of administration of viral immunogenic therapeutic agents, particularly diminishing host humoral immune response to such administration.
2. Background Art
A broad spectrum of human disease involves genetic aberrations at the cellular level. Some of these diseases include cystic fibrosis, anemia, hemophilia, diabetes, Huntington""s Disease, AIDS, abnormally high serum cholesterol levels, and certain immune deficiencies. In particular, a disease that has touched almost everyone""s lives is cancer. In spite of massive research efforts, only limited progress has been made in treating any of these diseases.
A number of new potentially promising therapies are currently under development. Gene therapy, in which a defective gene or sequence is supplanted with an exogenenous sequence, may be useful in treating not only cancer, but all of the previously listed diseases. Gene therapy generally requires a delivery vehicle for the exogenous sequence such as a viral vector. Newly developed viral agents that may be effective vectors against these diseases include retroviruses and recombinant adenoviruses. For review see Kim et al. (1996) Mol. Med. Today 12:519-527) and Smith et al. (1996) Gene Therapy 3:496-502. Other viral vectors that are potentially useful as therapeutic agents include Moloney mouse leukemia virus (MoMLV), Pox virus, Herpes virus, HIV and Adeno-associated viruses (AAV).
In addition, in the cancer context, more specific attenuated replication competent viral vectors have been developed, in which selective replication in cancer cells preferentially destroys those cells. Various cell specific replication competent adenovirus constructs, which preferentially replicate (and thus destroy) certain cell types, are described in commonly-owned U.S. patent application Ser. Nos. 09/033,555, 09/033,333, 60/076,545, and 09/033,556. Another attenuated replication-competent adenovirus is Onyx-015 adenovirus. Onyx-015 has a deletion in the E1B-55 kDa protein, which normally inhibits the cellular p53 tumor suppressor protein. Onyx-015 can replicate in p53-deficient human cells, but does not replicate efficiently in p53-positive cells. Bischoff et al. (1996) Science 274:373-376; Heise et al. (1997) Nat. Med. 3:639-645.
The favorable factors contributing to adenovirus as a safe therapeutic agent include: (a) infection with adenovirus has minor clinical disease manifestations; (b) adenovirus has a stable well-described and characterized genome; (c) adenovirus is unable to integrate its viral DNA into host DNA; (d) adenovirus allows transient gene expression; (e) adenovirus is able to infect both dividing and non-dividing cells; (f) adenovirus can infect a variety of human cell types; (g) adenovirus is physically stable, and (h) adenovirus is amenable to high titer production.
The adenovirus type 5 genome is a double-stranded DNA molecule of 35,935 base pairs containing short inverted terminal repeats. Chroboczek et al. (1992) Virology 186:280-285; Garon et al. (1972) Proc. Natl. Acad. Sci. USA 69:2391-2395. Expression of the genome is a regulated cascade which is arbitrarily divided into early (E) and late (L) phases, with viral DNA replication required for maximal L gene expression. Related RNA transcripts are grouped according to the region of the genome from which they are transcribed as well as by the timing (E or L) of their expression. The E3 region is not essential for replication in tissue culture and this region is deleted from most first-generation therapeutic adenovirus.
There are 47 different serotypes of adenovirus, which are distinguishable by antibody reactivity to epitopes on the virion surface. Each serotype is assigned to one of five Subgroups (A-E). Members of a Subgroup can exchange genetic material (recombine) efficiently, but they do not recombine with members of a different Subgroup. Adenovirus types 1, 2, 5, and 6 are members of Subgroup C. Adenovirus type 5 (the type typically used in gene therapy and for other therapies) is associated with a self-limiting, febrile respiratory illness and ocular disease in humans. In long-term immunosuppressed individuals, adenovirus 5 is also associated with renal impairment, hepatic necrosis, and gastric erosions. Shields et al. (1985) New England J. Med. 312:529-533; Zahradnik et al. (1980) Am. J. Med. 68: 725-732. Adenovirus 5 and the other Subgroup C viruses have little or no oncogenic potential in mammals. Horowitz (1990) in Virology, (Raven Press, New York, 2nd Ed.) pp. 1679-1721.
Use of viral therapeutic agents such as adenovirus holds promise, but there are a number of significant barriers to their effectiveness. Two of the major limitations of virus-based vectors as therapeutic vehicles are (a) the inactivation of virus by pre-existing circulating antibodies to the virus, and (b) the reduced efficacy of repeat dosage by primary or secondary induction of humoral immunity. For example, with respect to adenovirus, a recent serological survey indicates that 57% of the adult population in the U.S. has neutralizing antibodies to adenovirus 5 with titers ranging from 1:2 to 1:512. Schulick et al. (1997) J. Clin. Invest. 99:209-219. Neutralizing antibodies are generated to specific antigenic determinants within 7-14 days following intravenous adenovirus injection. Zinkernagel (1996) Science 271:173-178. These antibodies are typically specific for proteins on the virion, such as capsid proteins and various glycoproteins. George-Fries et al (1984) Virology 134(1):64-71; Fisher et al. (1997); Eing et al. (1989) J. Med. Virol. 27(1):59-65; Highlander et al. (1987) J. Virol. 61(11)3356-64; Durali et al. (1998) J. Virol. 72(5):3547-53. Activation of CD4+ lymphocytes by adenovirus capsid proteins also leads to the up-regulation of MHC class I molecules in infected cells contributing to the production of neutralizing antibodies as well as the clearing of adenovirus infected cells by CTLs. Yang et al. (1995) J. Virol. 69:2004-2015. For many patients, a therapeutic adenovirus will elicit an amnestic humoral response and a CTL response further decreasing the efficacy of repeat intravenous treatment with the same virus. Since the majority of the human population has been exposed to adenovirus during their lifetime, pre-existing immunity could be a major obstacle to the use of viral vectors. Such high prevalence of neutralizing antibodies to adenovirus in adult humans could inhibit adenovirus dissemination (to distant tumor sites for example) and greatly limit the effectiveness of adenovirus type 5-based therapy in vivo.
The effect of neutralizing antibodies on viral dissemination is a major issue in determining the success of viral therapy using parenteral administration, especially since intravenous administration may be desirable for treatment for metastatic disease or non-discrete tumors. Although recent studies have indicated that pre-existing antibody may not reduce the efficiency of intratumoral viral administration (in terms of tumor regression), virus dissemination appears to be greatly impeded by pre-existing circulating antibodies. One group found that transgene expression in the liver of adenovirus-immune animals following intratumoral injection was reduced more than 1000-fold compared to the transgene expression found in naive mice. Bramson et al. (1997) Gene Therapy 4:1069-1-76. In another example, in mice 90% of viral vectors is eliminated within 24 hours of intravenous injection. Worgall et al. (1997) Hum. Gene Ther. 8:37-44. This finding was confirmed by quantitative analysis of viral DNA in liver, spleen and lung using Southern analysis over the first 70 hours post injection demonstrating a 90% elimination of vector. Christ et al. (1997) Immunology Letters 57:19-25. Schulick et al. (1997) found if rats are immunized by prior intravenous exposure to adenovirus, a second intravenous injection of an adenovirus vector gave no evidence of recombinant gene expression three days after the attempted gene transfer. This observation could be reproduced even in the presence of low (i.e., 1:2) titers of neutralizing antibody to adenovirus. Schulick et al. (1997). Another group examined immune responses to an adenoviral vector and to the recombinant gene expression (xcex2-galactosidase protein) in four patients with lung cancer. Gahery-Segard et al. (1997) J. Clin. Invest. 100:2218-2226. In patient 1, a high level of neutralizing antibodies to adenovirus was detected before adenovirus-xcex2-gal injection (100% neutralization at 1:400), whereas it was low in patient 3 (30% neutralization at 1:400) and undetectable in the other two patients. Virus DNA was detected by PCR in tumor biopsies on day 30 and day 60 from all patients except patient 1. Thus, Recent studies have established that pre-existing humoral immunity poses a significant barrier to viral half-life, dissemination, and effectiveness and pre-existing anti-adenovirus neutralizing antibodies limit the therapeutic efficacy of adenovirus-mediated therapy through intravenous administration.
Strategies developed to address the problem of pre-existing immunity have significant limitations. Recently, a strategy has been developed for down-regulating pre-existing anti-adenovirus immunity by oral tolerization based on administration of adenoviral proteins. Ilan et al. (1997) J. Clin. Invest. 99(5): 1098-1106. But this strategy is not realistic, mostly due to the fact that this method is effective only in newborns.
Apheresis is a process by which certain blood components are removed extracorporeally and the blood is reintroduced into an individual. Typically apheresis is used to treat pathological conditions in which the component to be removed is associated with a particular disease state. Therapeutic apheresis procedures can rapidly remove abnormal blood cells or plasma constituents, and has been used to treat a number of hematologic diseases, including hyperleukocytic leukemias, lymphomas, thrombocythemia, thrombotic thrombocytopenic purpura, sickle cell anemia, and disorders associated with pathologic protein in plasma. The specific procedure could be chosen according to the blood element being removed: cytapheresis, for any blood cell removed; leukapheresis, lymphapheresis, erythrocytapheresis, plateletpheresis (thrombocytapheresis), plasma exchange (therapeutic plasmapheresis), and immunoapheresis. See, e.g., U.S. Pat. Nos. 4,851,126, 4,255,627, 4,086,294, 5,147,290, and 4,411,792.
Recently, affinity adsorption apheresis has been developed for treatment of autoimmune disorders such as hemophilia, idiopathic thrombocytopenia purpura, and lupus nephritis. Nilsson et al. (1981) Blood 58(1):38-44; Christie et al. (1993) Transfusion 33:234-242; Richter et al. (1997) ASAIO J. 43(1):53-59; Suzuki et al. (1994) Autoimmunity 19: 105-112; U.S. Pat. No. 5,733,254. ITP is generally characterized by the appearance of lesions resulting from hemorrhage into the skin, a decreased platelet count, increased megakaryocytes in the bone marrow and increased platelet-association IgG in the absence of drug exposure or toxic exposure. The most commonly used column is the staphylococcus protein A column with protein A as the ligand attached to the silica carrier. However, these columns adsorb immunoglobulin generally (with greatest affinity for IgG subclasses 1, 2, and 4, and lower affinity for IgG 3, IgM, and IgA) and immune complexes. Bandarenko (1996) Clinics in Laboratory Medicine 16:907-929. The PROSORBA(copyright) column (IMRÉ, Inc., San Diego, Calif.) contains protein A linked to silica and is approved for clinical use in the treatment of idiopathic thrombocytopenia purpura (ITP) and HIV-related ITP. Snyder et al. (1992) Blood 79:2237-2245; Christie and Howe (1993) Transfusion 33:234-242. Another significant limitation of commercially available Protein A columns (besides their relative non-specificity) is their limited binding capacity. Christie et al. (1993). An alternative approach involves the use of columns containing polyclonal anti-human IgG antibodies. Richter et al. (1993) Metabol. Clin. Exp. 42:888-894; Richter et al. (1997) ASAIO J. 43(1):53-59. However, these columns remove any IgG molecules and are thus not specific.
Other approaches have utilized THERASORB(copyright) (formerly manufactured by Baxter Corp, Munich, Germany) columns which was a general affinity column for conjugating an immunosorbent such as antibody. In a model of liver transplantation rejection, a more complete removal of IgG (95%) was found with the use of THERASORB(copyright) columns consisting of sheep-anti-human IgG antibodies covalently coupled to Sepharose CL-4B. Pascher et al. (1997) Transplantation 63(6):867-875. THERASORB(copyright) linked with antibodies against xcex21-adrenoreceptor antibodies was also used in the removal of autoantibodies in another study treating idiopathic dilated cardiomyopathy. Immunoapheresis resulted in an autoantibody level to 8% of original values. Wallukat et al. (1996) Int""l J. Card. 54:191-195.
Other experimental applications of affinity apheresis include: the depletion of anti-factor VIII antibodies in the management of hemophilia (Nilsson et al. (1981) Blood 58:38; Watson et al. (1989) Cancer 64:1400); the removal of cationic anti-DNA antibodies associated with lupus nephritis with polyanionic compounds immobilized on a cellulose column (Suzuki et al. (1994) Autoimmunity 19:105-112); the depletion of low-density lipoprotein (LDL) from patients with familial hypercholesterolemia by linking anti-apolipoprotein B to Sepharose (Richter et al. (1993) Metabol. Clin. Exp. 42: 888-894; Suzuki et al. (1995) Artificial Organs 20(4):296-302); the removal of anti-basement membrane antibodies in the treatment of Goodpasture""s syndrome (Bandarenko (1996) Clinics in Laboratory Medicine 16:907-929); and the treatment of cisplatin and mitomycin C-induced hemolytic uremic syndrome/thrombotic thrombocytopenia purpura (HUS/TTP) (Watson et al. (1989) Cancer 64:1400; Snyder et al. (1993) Cancer 71:1882-1892).
The use and efficacy of viral immunogenic therapeutic agents that promote target specific treatment can be limited by the body""s own immune system. The current invention addresses this limitation by providing methods to enhance performance of therapeutic viral vectors by partially pre-empting the body""s immune defenses.
All publications cited herein are hereby incorporated by reference in their entirety.
The present invention provides methods and compositions for reducing pre-existing humoral immunity to immunogenic viral therapeutic agents.
Accordingly, in one aspect, the invention provides methods of reducing pre-existing humoral immunity to a viral immunogenic therapeutic agent in an individual comprising treating (i.e., contacting) the individual""s blood extracorporeally with an immunosorbent that selectively binds anti-virus antibody to the viral therapeutic agent; removing antibody-immunosorbent complexes formed during the treatment, if any; and returning the blood to the individual. The viral immunogenic therapeutic agent may be any of a number of viruses such as adenovirus. The immunosorbents may be any of a number of substances which specifically bind to the antibody, such as organic molecules and polypeptides. Viral surface proteins are preferred.
In another aspect, the invention provides methods of reducing pre-existing humoral immunity to a viral immunogenic therapeutic agent in an individual comprising selectively removing antibody which specifically binds to the viral immunogenic agent from blood of the individual, wherein the antibody is selectively removed by extracorporeally binding the antibody to an immunosorbent which specifically binds to the antibody; removing immunosorbent-antibody complexes, if any; and returning the blood to the individual.
In another aspect, the invention provides methods of administering a viral therapeutic agent to an individual, comprising the steps of: (a) treating the individual""s blood extracorporeally with an immunosorbent that binds antibody; (b) removing antibody-immunosorbent complexes formed during the treatment, if any, from the blood; (c) returning the blood to the individual; and (d) administering the viral therapeutic agent to the individual.
In another aspect, the invention provides kits for use in conjunction with these methods (i.e., for selective removal and/or detection of anti-virus antibody) comprising an immunosorbent that specifically binds the antibody to be removed in suitable packaging.
In another aspect, the invention provides compositions for selectively removing antibody which specifically binds to a viral immunogenic agent from blood of the individual, comprising an immunosorbent which specifically binds to the antibody conjugated to a matrix.